Caractéristiques géotechniques du secteur du Parc Olympique, Montréal

Abstract

Under natural conditions, the western limit of the Olympic Park site along Sherbrooke Street is formed by a terrace of marine clay deposited in the Champlain Sea. This terrace has an average height of 60 ft (18 m) and overlies shallow fine grained deposits of fluvio–glacial or glacial origin, which are encountered at ground surface in the eastern part of the site. The bedrock, of Ordovician age, is part of a monoclinal structure which dips at 3° to 5° towards the northeast; bedding planes and vertical fractures form the main planes of discontinuity. The surficial part of the bedrock has been strongly disturbed by the action of glaciers during the Wisconsin glaciation: a displaced rock slab now covers the main part of the site and has greatly affected the design of the foundations for the various structures.Geotechnical investigations carried out by the City of Montreal on or near the site for earlier tunneling projects were used to establish a geotechnical map of the Olympic Park site. Based on this map, the foundation elevations for the different buildings, the type of earth supporting structures, and the geometry of cut slopes could be selected. Along Sherbrooke Street, 70 ft (21 m) deep excavations were necessary in an area where lateral movements could not be tolerated. Consequently a program for monitoring the cast-in-place diaphragm retaining wall and the slopes was carried out by the City of Montreal with the participation of the Ecole Polytechnique de Montréal. [Journal translation]